JP4032293B2 - Ultrasound-magnetic resonance combined medical device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to a technique of an ultrasonic-magnetic resonance composite medical device that combines ultrasonic imaging and / or ultrasonic therapy and magnetic resonance imaging.
[0002]
[Prior art]
The ultrasonic imaging apparatus irradiates a subject with ultrasonic waves from a probe, receives a reflected signal of an ultrasonic wave generated from the inside of the subject, and the inside of the subject is a two-dimensional or three-dimensional image based on a difference in acoustic characteristics. For diagnosis and treatment, for example, by imaging information such as blood flow velocity. On the other hand, a magnetic resonance imaging apparatus (MRI apparatus) excites specific nuclei such as hydrogen (proton) and phosphorus which are main substances constituting a subject by applying a high-frequency magnetic field pulse to the subject in a static magnetic field, The nuclear magnetic resonance signal generated thereby is received, and for example, the proton density distribution and the spatial distribution of the relaxation phenomenon of the excited state are imaged two-dimensionally or three-dimensionally, or various biological information is imaged for diagnosis and treatment. .
[0003]
These ultrasonic imaging apparatuses and MRI apparatuses are widely used as medical apparatuses, and developments in application fields are progressing. For example, monitoring of invasive devices such as catheters, monitoring of therapeutic instruments that perform treatment by inserting laser fibers or microwave electrodes into the lesion, techniques for observing the therapeutic effects, and focused ultrasound from outside the subject Ultrasound treatment, in which heat treatment is performed by irradiating the lesion area, etc. have been proposed.
[0004]
[Problems to be solved by the invention]
By the way, in an ultrasonic medical device, an ultrasonic probe for imaging or treatment can be held by hand and applied to the body surface of a subject, and a tomographic image of a part to be observed can be arbitrarily selected while moving or tilting the probe. In addition, since the direction of the therapeutic ultrasonic beam can be adjusted to the lesion site, it is extremely excellent in operability.
[0005]
However, since ultrasonic imaging requires operation by placing the ultrasonic probe on the outer surface of the subject, the operation range of the position and tilt of the ultrasonic probe is limited, and a tomographic image at an arbitrary position and direction is captured. For example, there is a drawback that a tomographic image of a blood vessel at a desired site cannot be obtained.
[0006]
In addition, the ultrasonic treatment is a so-called non-invasive treatment in which treatment is performed by irradiating a living body with an ultrasonic beam stronger than imaging from an ultrasonic probe and heating the affected part, so that the burden on the patient is reduced. There is an advantage of less.
[0007]
However, since ultrasonic imaging cannot accurately measure the position (especially depth) of a lesioned part, a technique for accurately matching the convergence position of a high-intensity therapeutic ultrasound beam to the lesioned part becomes a problem. In other words, even if the imaging probe can be moved or tilted by hand to find the lesion, it is difficult to measure the three-dimensional position of the lesion, particularly the depth of the lesion. The depth cannot be adjusted accurately.
[0008]
On the other hand, when a lesion is treated with a laser or microwave, since the laser fiber or microwave electrode is in contact with the lesion, for example, the tip of the laser fiber is included as an imaging section by MRI imaging or the like. Thus, the treatment site is included in the imaging section.
[0009]
In short, it is relatively easy to set the imaging section of MR imaging on the image, but in the case of ultrasonic therapy, the treatment site and the ultrasonic probe are separated from the inside and outside of the subject. Cannot be applied as is. Therefore, it is necessary to determine the convergence position of the ultrasonic beam by some method, set the convergence position on the MR image or the like by any method, and take an imaging section including the position by MRI.
[0010]
However, since the depth of convergence of the ultrasound beam varies depending on the radius of curvature of the treatment probe, the ultrasound delay time between each transducer, the ultrasound frequency, etc. Mistakes and highly skilled knowledge are necessary, and it is a complicated task for a surgeon who performs treatment and diagnosis.
[0011]
Similarly, in ultrasound imaging, since the resolution of the image depends essentially on the wavelength of the ultrasound, the boundary of the tissue becomes unclear, so it is necessary to accurately measure the boundary and size of the lesion. May be a problem for treatment. In addition, establishment of a technique for measuring the effect of treatment on a site subjected to ultrasonic treatment is desired.
[0012]
On the other hand, the MRI apparatus has a high contrast resolution. Currently, a resolution of 256, 512, etc. is used, and a resolution of 1024 has been tried in part, so that the boundary of the tissue can be clearly imaged. Further, the MRI apparatus can arbitrarily set the position and orientation of the imaging cross section as compared with the ultrasonic imaging, and can capture a desired vascular tomographic image. In addition, in view of the fact that the T1 relaxation time and the T2 relaxation time correlate with the temperature, or the resonance frequency correlates with the temperature, it is possible to measure the temperature change of the specific part by measuring them. Different biological information can be obtained.
[0013]
However, the imaging section in the case of the MRI apparatus is inferior in operability compared to ultrasonic imaging, for example, an operation for setting a parameter related to the imaging section of the imaging sequence must be performed on the image.
[0014]
Accordingly, an object of the present invention is to realize a composite medical apparatus that is excellent in operability and functionality by combining the advantages of an ultrasonic medical apparatus and an MRI apparatus.
[0015]
[Means for Solving the Problems]
The present invention solves the above problems by the following means.
[0016]
The present invention is intended to enhance functionality by combining an ultrasonic medical apparatus and a magnetic resonance imaging apparatus while maintaining the operability of the ultrasonic medical apparatus. That is, the ultrasonic probe is driven to irradiate the subject with imaging ultrasonic waves, and the US control means for processing the ultrasonic signal received by the ultrasonic probe, and the reception-processed ultrasonic signal An ultrasonic medical apparatus having a US image generation means for generating a tomographic image based on it and an imaging sequence for applying a gradient magnetic field and a high frequency pulse to a subject placed in a static magnetic field according to a set tomographic plane A magnetic resonance imaging apparatus comprising: an MR control means for performing the imaging sequence; and an MR image generation means for generating a tomographic image based on a nuclear magnetic resonance signal generated from the subject by execution of the imaging sequence. Basic. In this case, the display means for displaying the images generated by the US image generation means and the MR image generation means may be provided individually or shared.
[0017]
In particular, the present invention receives a detection pointer of a position and orientation fixed to an ultrasonic probe, a reference pointer fixed to an apparatus main body of the magnetic resonance imaging apparatus, the detection pointer, and the reference pointer. A compound eye camera, and probe position calculation means for converting the position and orientation of the ultrasonic probe into a coordinate system (hereinafter referred to as MR coordinate system) of the MRI apparatus based on image data received by the compound eye camera. To do. That is, since the reference pointer is fixed to the MRI apparatus main body, the coordinate system of the reference pointer and the MR coordinate system of the static magnetic field space where the subject is placed uniquely match. Therefore, the MR control means can recognize the position and orientation of the ultrasonic probe in the MR coordinate system by the probe position calculation means.
[0018]
As a result, for example, by acquiring the focal position of the imaging ultrasonic beam from the US control unit, a cross section in an arbitrary direction including the focal position can be easily set as the imaging cross section. In this case, the set tomographic plane of the MR image is determined based on the position and orientation of the ultrasonic probe converted by the probe position calculating means and the focal position of the ultrasonic probe output from the US control means. can do. In addition, the determined set fault plane Provide cooperative control means for outputting to the MR control means be able to . This cooperative control means can be realized by a personal computer.
[0019]
In particular, when a lesion is detected by operating an ultrasound imaging probe, the tomographic plane direction of the US tomogram is determined from the position and orientation of the imaging probe at that time, and the depth of the lesion is determined by the focal position of the imaging probe at that time. The three-dimensional position of the lesion can be obtained. That is, the MR control means executes the imaging sequence for the set tomographic plane passing through the lesion site that is the focal position of the imaging probe. And MR control means detects the position of a lesion part accurately based on the acquired MR tomogram. Next, the position of the convergence point of the therapeutic ultrasound beam is calculated from the MR tomographic image data based on the detected position of the lesioned part, and the calculated convergence point position is output to the US control means. Thus, the US control means controls the convergence point of the therapeutic ultrasonic beam. As a result, a therapeutic ultrasonic beam can be accurately irradiated onto the lesioned portion, so that the operability of the treatment is improved. In addition, since the MR tomographic image is switched following the position and inclination of the treatment probe, it is only necessary to adjust the position and inclination of the treatment probe so that the lesion is displayed on the MR image. A therapeutic ultrasound beam can be irradiated.
[0020]
Further, the MR control means executes an imaging sequence for the set tomographic plane passing through the lesion, detects a mark representing a treatment point input and set in the MR tomographic image displayed on the display means, and executes the imaging sequence. The position of the convergence point of the therapeutic ultrasound beam may be calculated from the image data based on the position, and the calculated convergence point position may be output to the US control means.
[0021]
Further, the US control means controls the convergence point position of the therapeutic ultrasonic beam based on the input convergence point position of the therapeutic ultrasonic beam, and responds to a given command from the ultrasonic probe for therapeutic use. In accordance with this, the MR control means outputs the convergence point position of the therapeutic ultrasound beam to the US control means, and then captures a T1 or T2-weighted image for the tomographic plane including the convergence point. It is preferable to execute the sequence. Further, it is preferable that the MR control means measures a temperature change of the MR tomogram based on the image data of the T1 or T2 weighted image and displays a color mapping image on the display device according to the temperature change. Thereby, the surgeon can easily confirm the effect of the treatment.
[0022]
Further, while allowing an operator to observe a desired US tomographic image using an ultrasonic imaging probe, changes in the position and posture of the US tomographic image are obtained by detecting changes in position and posture associated with the movement of the imaging probe. The MR image of the same cross section can be taken in accordance with the position change of the US tomographic image.
[0023]
Specifically, the US control unit takes in the coordinate data of the position and orientation of the ultrasonic probe converted into the MR coordinate system output from the cooperative control unit, and MR coordinate data into the image data of the ultrasonic three-dimensional tomographic image. The MR control means executes an imaging sequence for imaging an MR three-dimensional image of a region corresponding to the ultrasonic three-dimensional tomographic image, and a specific tissue (for example, based on the picked-up MR three-dimensional image) And the image data relating to the boundary can be output to the display unit and displayed on the ultrasonic three-dimensional tomographic image. According to this, it is possible to complement an ultrasonic tomographic image with a poor resolution of the boundary of an organ or the like, and to clearly display the boundary of the organ with an MR image.
[0024]
Further, based on the boundary of a specific tissue such as an organ obtained in the same manner, the US control means extracts pixel data of an ultrasonic three-dimensional tomographic image within the boundary and displays it on the display means. You can also According to this, it is possible to remove a signal from a tissue other than the organ and to improve the image quality inside the organ.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of an ultrasonic-magnetic resonance composite medical device (hereinafter abbreviated as US-MR composite medical device) of the present invention.
[0026]
First, the ultrasonic medical device will be described. The ultrasonic probe 1 is formed so that an imaging probe 2 and a treatment probe 3 are integrally formed and operated by holding the probe support portion 4 by hand. The imaging probe 2 is formed by arranging a plurality of transducers in one or a plurality of rows, for example, as in a convex type, similar to that used in a known ultrasonic diagnostic apparatus. The treatment probe 3 is formed by dividing a plurality of transducers on both sides of the imaging probe 2 and arranging them symmetrically so as to form a concave curved surface. In this embodiment, the arrangement directions of the imaging probe 2 and the treatment probe 3 are orthogonal to each other, but the present invention is not limited to this.
[0027]
The therapeutic probe 3 is supplied with the ultrasonic pulse generated by the therapeutic pulse generation circuit 11 via the therapeutic wave convergence circuit 12 and the amplifier 13. That is, the therapeutic wave convergence circuit 12 appropriately delays the ultrasonic wave supplied to each transducer, thereby controlling the convergence point (focal point) of the ultrasonic beam emitted from the therapeutic probe 3 to a desired position and the amplifier 13. Is converted into a high-energy drive pulse and supplied to each transducer.
[0028]
On the other hand, an imaging ultrasonic pulse generated from the imaging pulse generation circuit 21 is focused in the imaging wave convergence circuit 22, amplified in the amplifier 23, and then supplied to the imaging probe 2 via the transmission / reception separator 24. Is done. The ultrasonic reception signal received from the living body by the imaging probe 2 is guided to the amplifier 25 via the transmitter / receiver separator 24 and amplified, and then subjected to phasing processing in the ultrasonic (US) signal processing unit 26. . The ultrasonic (US) image generation unit 27 generates an ultrasonic tomographic image based on the reception signal output from the US signal processing unit 26. The generated tomographic image is displayed on the US monitor 28. The therapeutic pulse generation circuit 11, the therapeutic wave convergence circuit 12, the imaging pulse generation circuit 21, the imaging wave convergence circuit 22, the US signal processing unit 26, and the US image generation unit 27 are commands of the US control unit 30 formed by a computer. Controlled by. Further, the operator can set various diagnostic conditions and treatment conditions by inputting a command to the control unit 30 from the operation device 31.
[0029]
Next, the magnetic resonance imaging (MRI) apparatus will be described. The MRI apparatus includes an MR apparatus main body 41, an MR control unit 42 for controlling the MR apparatus main body 41, an MR operation unit 43 for inputting a command to the MR control unit 42, and a nuclear magnetic resonance signal output from the MR apparatus main body 41. An MR signal processing unit 44 that processes the MR image, an MR image generation unit 45 that reconstructs an MR image based on the processed nuclear magnetic resonance signal, and an MR monitor 46 that displays the reconstructed MR image. It is configured.
[0030]
The MR apparatus main body 41 preferably employs a so-called open type MRI apparatus shown in FIG. The illustrated example is a vertical magnetic field type permanent magnet MRI apparatus. The concept of a typical MR apparatus main body will be described with reference to FIG. The MR apparatus main body includes a magnet 402 that generates a static magnetic field around the subject 401, a gradient magnetic field coil 403 that applies a gradient magnetic field to the static magnetic field space, an RF coil 404 that applies a high-frequency magnetic field pulse to this region, An RF coil 405 for detecting an NMR signal generated by the subject 401 is provided. The gradient magnetic field coil 403 is composed of gradient magnetic field coils in the X, Y, and Z-axis directions, and each generates a gradient magnetic field in response to a signal from the gradient magnetic field power supply 409. The RF coil 404 generates a high frequency magnetic field by a high frequency magnetic field pulse supplied from the RF transmission unit 410. The open type MRI apparatus main body 41 of FIG. 2 also has the same function. The nuclear magnetic resonance signal received by the RF coil 405 is input to the MR signal processing unit 44 in FIG. 1, and the gradient magnetic field power source 409 and the RF transmission unit 410 are controlled by the MR control unit 42 in FIG. The MR control unit 42 drives and controls the MR apparatus main body 41 according to the imaging sequence to capture a desired MR tomographic image.
[0031]
Next, a cooperative control apparatus for an ultrasonic medical apparatus and an MRI apparatus according to features of the present invention will be described. The cooperative control device includes a position detection device that detects the position and orientation of the ultrasonic probe. A position detection device (for example, POLARIS (trade name) of Northern Digital Instrument Co., Ltd. is applied) includes a detection pointer 51 fixed to the ultrasonic probe 1, a reference pointer 52 fixed to the MR apparatus main body 41, and an infrared ray. A compound eye camera 53 having two cameras and a probe position calculation means 54 are provided.
[0032]
As the position detection device, there are an active type and a passive type. Each of the active type detection pointer 51 and the reference pointer 52 has at least three infrared light emitting diodes as markers, and the markers are positioned at, for example, the apex of a triangle. It is formed fixed to a support. In the case of the bass type, each of the detection pointer 51 and the reference pointer 52 is formed by using at least three reflecting spheres (for example, a diameter of 10 mm) as markers and fixing the markers to the support, for example, at the apex of the triangle. The The compound-eye camera 51 is formed by attaching a light emitting diode.
[0033]
The compound eye camera 51 continuously receives the detection pointer 51 and the reference pointer 52 and outputs the received data to the probe position calculation means 54. The probe position calculation means 54 detects the three-dimensional position of each marker in real time, and detects the six-dimensional movement of the detection pointer 51 based on this. The detected 6-dimensional movement can also be output and displayed. The position measurement accuracy is equivalent (for example, 0.35 mm) to the active type and the passive type, and the display switching speed is 20 to 60 Hz. The passive type is easy to use because it does not require a line for supplying power to the pointer.
[0034]
The six-dimensional movement of the detection pointer 51 detected by the probe position calculation means 54, that is, the detection data of the position and orientation of the detection pointer 51 is input to the cooperative control means 55. As will be described later, the cooperative control unit 55 takes in the focal depth of the ultrasonic probe 1 from the US control unit 30 and sets a tomographic plane passing through the focal position based on the detection data of the position and orientation of the detection pointer 51. To the MR control unit 42. The direction of the tomographic plane at this time may coincide with the direction of the tomographic plane of the ultrasonic probe 1 or can be set to an arbitrary direction designated by the operator.
[0035]
When such a position detection apparatus is applied to a US-MR combined medical apparatus using an open MRI apparatus, the arrangement configuration shown in FIGS. 2 and 3 is preferable. That is, the reference pointer 52 is fixed to the front and back surfaces of the gantry 41a of the MR apparatus main body 41. Thereby, the coordinate system of the reference pointer 52 can be uniquely matched with the MR coordinate system of the static magnetic field. The compound eye camera 53 is provided by being suspended from a support arm 53a composed of a plurality of arms connected to an arm that is rotatably supported at the center of the top of the gantry 41a. Thereby, as shown in the plan view of FIG. 3, the compound-eye camera 53 can be moved to an arbitrary position in an arc-shaped region centered on the gantry 41a.
[0036]
In FIG. 3, the operator 100 is provided with a detection pointer 51 fixed to the grasped ultrasonic probe 1. The ultrasound probe 1 is connected to the ultrasound apparatus main body 33 so that tomographic imaging or treatment of a desired part of the subject 401 can be performed by the operation of the operator 100. In addition, the MR monitor 46 is provided suspended from a support arm 46a composed of a plurality of arms rotatably supported on the top of the gantry of the MR apparatus main body 41.
[0037]
A detailed configuration of the cooperative control means 55 of the US-MR composite apparatus configured as described above will be described below together with an operation example.
(Embodiment of ultrasonic therapy)
As shown in FIG. 2, the operator 100 holds the ultrasonic probe 1 in his hand and applies it to the subject 401. In this case, the ultrasonic probe 1 may be supported and fixed by a nonmagnetic support member. Then, the operator 100 operates the position and inclination of the ultrasonic probe 1 to determine the imaging section of the subject 401 and starts ultrasonic imaging. Thereby, a tomographic image is displayed on the US monitor 28. The surgeon 100 searches for a lesion to be treated while changing the position and posture of the ultrasonic probe 1. At this time, the position and orientation of the detection pointer 51 are detected based on the received image data output from the compound eye camera 53 by the probe position calculation means 54.
[0038]
The cooperative control means 55 takes in the focal depth of the imaging probe 2 at that time from the US control unit 30, and calculates the three-dimensional position of the lesion recognized by the operator from the position, posture and focal depth of the detection pointer 51 by MR coordinates. Calculate for the system. Then, a command is output to the MR control unit 42 so as to capture an MR image of the tomographic plane in the same direction as the ultrasonic tomographic image, including the lesioned part. The MR imaging section can be selected from a section parallel to the ultrasound probe 1, the same plane as the ultrasound beam, or a section perpendicular to the section by an operation switch provided in the ultrasound probe 1 or the US controller 31 or the like. . Thereby, the surgeon can monitor while switching the cross section according to the case or lesion site.
[0039]
The MR control unit 42 determines the tomographic plane of the imaging sequence as the set tomographic plane instructed from the cooperative control means 55, and drives and controls the MR apparatus main body 41. Thereby, a tomographic image including a lesion part recognized by the operator 100 is displayed on the MR monitor 46. Usually, the lesion is spherical or elliptical with a diameter of 2 to 3 cm. This MR imaging process is performed in real time following the movement of the ultrasonic probe 1. That is, the surgeon 100 can set the MR tomographic plane freely and easily by moving the ultrasonic probe 1.
[0040]
For example, a fluoroscopic sequence is applied as the MRI imaging sequence, and the command of the set cross section output from the cooperative control means 55 is updated every 0.5 seconds, for example, and reflected in the MRI tomographic image. As the imaging sequence, a well-known TRSG sequence, SG sequence, multi-shot EPI, or other fluoroscopic sequence can be applied. In these sequences, the image can be updated every 0.5 to 4 seconds. A typical slice thickness of the MR image is about 8 mm.
[0041]
In this way, when the surgeon 100 moves the ultrasonic probe 1, an MR tomographic image including a lesion is displayed on the MR monitor 43. On the other hand, according to this MR tomogram, the depth of the affected part from the body surface can be obtained with high accuracy. Therefore, the MR control unit 42 calculates the distance from the body surface to the lesioned part on the basis of the tomographic plane of the ultrasonic probe 1 and outputs it to the cooperative control means 55. The cooperative control means 55 transfers the distance to the US control unit 30 as the convergence point data of the therapeutic ultrasonic beam.
[0042]
The US control unit 30 issues a command to the therapeutic wave convergence circuit 12 according to the convergence point data of the therapeutic ultrasonic beam, and controls the convergence position of the ultrasonic beam irradiated from the therapeutic probe 3. That is, the transducer (piezoelectric element) of the treatment probe 3 is arranged in an arc shape with a curvature R as shown in FIG. 5, and the ultrasonic beam converges at a convergence point distance F. This distance F is inside the subject 401 and is adjusted to, for example, a lesion. The distance F of the convergence point can be adjusted by changing the timing time of the ultrasonic wave supplied to each transducer in the therapeutic wave delay circuit 22.
[0043]
In this state, the operator 100 stops the movement of the ultrasonic probe 1 and irradiates the lesioned part with convergent ultrasonic waves to perform local heat treatment. Thus, the treatment can be easily performed by aligning the convergence point of the therapeutic ultrasonic beam with the lesion and heating the site. The irradiation of the ultrasonic beam from the treatment probe 3 is transmitted to the MR control unit 42 via the US control unit 30 or the cooperative control means 55.
[0044]
In response to this, the MR control unit 42 executes an imaging sequence of, for example, a T1-weighted image or a T2-weighted image on the same cross section, and sends a command to the MR signal processing unit 44 and the MR image generation unit 45, thereby causing a lesion area. A temperature distribution image is generated by obtaining a temperature distribution change in a region including the. The temperature distribution image is displayed on the MR monitor 46. In the case of the present embodiment, it is preferable to repeatedly capture a T1 weighted image or a T2 weighted image in about 2 to 7 seconds, and the photographing matrix is generally 128 × 128 to 256 × 256. Thereby, the operator 100 can easily confirm the effect of the ultrasonic treatment on the image. As a result, it is possible to avoid applying treatment to unnecessary parts, and to check the cooling of the heated part by treatment and sequentially treat adjacent lesions, so that the lesions can be treated without omission. it can. Further, after the treatment, MRI imaging can be performed to determine whether or not a lesion (for example, a tumor) has disappeared.
[0045]
As described above, according to the ultrasonic therapy method of the present embodiment, functions such as the high resolution of the MRI apparatus, the accuracy of distance measurement, and the temperature measurement without losing the operability of the ultrasonic medical apparatus. It is possible to realize an easy-to-use treatment device by using organically.
[0046]
As shown in FIG. 3, the compound-eye camera 53 is suspended by a support arm 53a at a position 1 to 1.5 m away from the center of the magnetostatic field generation region of the MR apparatus main body 41, and can be freely oriented and positioned. It is preferable to be able to change. Accordingly, it is possible to prevent the surgeon's operation from being hindered, and the compound eye camera 53 can be moved so that the detection pointer 51 and the reference pointer 52 are not behind the surgeon or the surgical instrument. That is, the two fan-shaped regions 57 and 58 shown in the figure are ranges in which both the detection pointer 51 and the reference pointer 52 can be stably detected from the compound eye camera 53. The range of 170 to 293 cm is appropriate for the radius of the sector regions 57 and 58. The height of the compound eye camera 53 is appropriately about 95 to 107 cm. The support arm 53a is formed so that the camera operates within this range. The update period of the received image data sent from the compound eye camera 53 to the probe position calculation means 54 is preferably about 2 to 20 sets / second. This image reception data is transmitted from the compound-eye camera 53 through an optical fiber cable, thereby preventing noise from being mixed in the MR apparatus.
[0047]
In FIG. 3, the position of the compound eye camera 53 was examined only on one side of the bed of the MR apparatus main body. However, since the MRI apparatus has an asymmetric two-pillar configuration, the operator can access the subject from the opposite side of the bed. it can. In that case, the compound eye camera 53 can be moved to the opposite side of the bed. Correspondingly, it is preferable to install a reference pointer 59 on the opposite side of the bed separately from the reference pointer 52 described above. In this case, it is preferable that the relative positions of the three markers (reflecting spheres) of the reference pointers 52 and 59 are arranged differently. Thereby, the compound eye camera 53 can identify which reference pointer is receiving the image. In response to this, the probe position calculation means 54 can automatically read out the position of the identified reference pointer from the memory, and can automatically obtain the imaging section data in the MR coordinate system.
[0048]
By the way, the example using the ultrasonic probe 1 provided with both the imaging probe 2 and the treatment probe 3 was shown in the ultrasonic therapy apparatus of embodiment of FIG. However, since the MRI apparatus is provided as the imaging apparatus, the imaging probe 2 can be omitted. That is, it is assumed that the ultrasonic probe 1 of FIG. 1 is provided with only the therapeutic probe 3, and the imaging function is omitted in accordance with this. Then, the MR tomographic image is displayed on the MR monitor 46 (or the US monitor 28) by the MRI apparatus according to the position and orientation of the ultrasonic probe 1 detected by the position detection apparatus. The surgeon searches for the lesion part exclusively based on the MR image, and designates the lesion part to be treated with a marker or the like on the MR monitor 46 (or US monitor 28). As a result, the MR control unit 42 calculates the three-dimensional position of the designated marker, particularly the distance from the body surface with which the ultrasonic probe 1 is in contact to the lesioned part, and sends it to the cooperative control device 55. The cooperative control means 55 calculates the convergence position of the ultrasound probe 1 based on the distance from the body surface to the lesioned part and sends it to the US control unit 30. In response to this, the US control unit 30 can send a command to the treatment wave convergence circuit 12 so that the convergence position of the treatment ultrasonic beam is aligned with the lesioned part.
[0049]
In addition, the intensity of the ultrasonic beam of the treatment probe 3 can be lowered to the imaging level, and the configuration similar to the embodiment of FIG. In this case, the resolution of the ultrasonic imaging image is lowered, but it may be sufficient for searching the position of the lesioned part.
(Method for generating ultrasonic three-dimensional image)
While an operator images a desired ultrasonic (US) three-dimensional image using an ultrasonic imaging probe, MR3 corresponding to the US three-dimensional image is detected by detecting a change in position and posture associated with the movement of the imaging probe. A three-dimensional image can be taken and a superior point of these three-dimensional images can be combined to create a three-dimensional image significant for diagnosis and provided to the operator. For example, the boundary portion of each tissue can be detected from the three-dimensional image data of MRI, and the boundary coordinates can be obtained to form the boundary of the three-dimensional image of the US image.
[0050]
A specific embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 is a diagram for explaining an operation method of the ultrasonic probe 1 when capturing a US three-dimensional image. As shown in FIG. 5A, the US image is moved to a plurality of three-dimensional positions (xi, yi, zi) (x) while moving the ultrasonic probe 1 substantially parallel along the body surface of the subject not shown. However, i is a natural number of 1 to n), and imaging of a plurality of sheets a1 to an is executed. Thus, each US image data imaged is stored in the memory. In this case, the probe position calculation means 54 determines the three-dimensional position and direction of the US tomographic image (hereinafter referred to as US tomographic image position data) based on the detection pointer 51 fixed to the ultrasonic probe 1 and the received image data of the reference pointer 52. Is transferred to the MR coordinate system and transferred to the US control unit 30 via the cooperative control means 55. The US control unit 30 stores US tomographic image position data in association with each US tomographic image. As shown in FIG. 6B, the same applies to the case where the posture (inclination angle) is changed without changing the position of the ultrasonic probe 1 and three-dimensional imaging is performed.
[0051]
On the other hand, the MRI apparatus captures a known T1-weighted image or T2-weighted image. For example, a fast spin echo method or a gradient echo method is used for the imaging sequence. The number of pixels is, for example, 256 × 256 × 256. In this case, a typical spatial resolution is 1 mm. In the MR image, the contrast for each organ (tissue) is different due to the different T1 value or T2 value. By utilizing this fact, an organ can be extracted by a known region growing method. That is, a specific organ portion is extracted from the MR image using the fact that the pixel values differ for each tissue. As a result, the pixel numbers of the edges of the extracted organ or tissue are obtained. This pixel number can be associated with the MR coordinate system on a one-to-one basis.
[0052]
By the way, the probe position calculation means 54 can associate the pixel position (number) on the US image with the pixel number of the MR coordinate system on a one-to-one basis. Therefore, it is possible to determine which position on the US image the edge of the organ extracted on the MR image is.
[0053]
For example, as shown in FIG. 7A, it is assumed that imaging is performed by operating the ultrasonic probe 1 on the three-dimensional region 71 of the subject 401, and the US three-dimensional image shown in FIG. 7B is acquired. A reference point 71a of the three-dimensional area 71 is set. On the other hand, the same region 71 is imaged by the MRI apparatus, and an MR three-dimensional image shown in FIG.
[0054]
Based on the MR three-dimensional image, a tomogram display designation line 72 is set to determine an arbitrary slice cross section. Based on this, the US tomographic image and the MRI tomographic image set in the tomographic image display designation line 72 are imaged. Thereby, a tomographic image including the organ 73 can be displayed on the display monitor.
[0055]
In this display, for example, the US tomographic image is displayed in gray scale. Then, the marginal image of the organ 73 of the MR tomogram is displayed in a different color (for example, yellow) in a semi-transparent manner and superimposed on the US tomogram. As a result, the observer can easily identify the outline of the organ that could not be identified in the ultrasonic tomogram. Therefore, the observer can observe information specific to ultrasonic imaging (for example, information on the elastic modulus of the local region, information on the Doppler phenomenon due to blood flow) and the like on the same screen in addition to the outline of the organ, diagnosis, etc. Convenient to.
[0056]
Further, a US three-dimensional image obtained by extracting only the pixels inside the organ 73 of the US image is subjected to a partial MIP (Maximum Intensity Method) process or a partial volume rendering process to obtain a US image in the target organ. Can be displayed in a form including three-dimensional information. According to this, it is possible to remove data with a low signal value in the deep part of the living body in the US image and data with a high signal near the skin, and it can be expected to improve the image quality by removing those noise components. Note that MIP processing or partial volume rendering processing is image processing that is widely performed on MRI and CT images.
(Other variations)
The RF coil 405 shown in FIG. 4 has been developed in various shapes, and can be used depending on the imaging region and the imaging purpose. For example, the surface coil is an RF coil that images a local site with high sensitivity. Conventionally, a local coil is used for imaging a part such as an ear, a temporomandibular joint, or a limb joint that requires high image quality in a small field of view. In addition, a multiple array coil (also called a phased array coil) has been developed in which a plurality of small surface coils are arranged adjacent to each other to achieve high sensitivity and field expansion. For normal head photography and abdominal photography, a volume coil with a wide field of view and a relatively uniform sensitivity distribution is used. For this, a multiple element resonator, a slotted tube resonator, and a solenoid coil are known.
[0057]
An open type MRI apparatus is used for so-called I-MRI (Interventiona1 MRI, Intraoperative MRI) used for surgery, puncture, and percutaneous treatment. Open MRI includes a double donut type, a C type, and an asymmetric two-post type. The double donut type has a structure in which two donut-shaped magnets that generate a horizontal magnetic field are arranged with a gap therebetween, and the subject is imaged between the gaps. The C type and the asymmetric two-post type generate a static magnetic field in the vertical direction with a hamburger type magnet. The most open type is an asymmetrical two-column type, which can be accessed from the left and right directions of the subject and the three directions on the parietal side.
[0058]
A technique for interactively setting an MRI imaging section is known as interactive scan control. That is, in puncture monitoring at the time of surgery using MRI, cardiac imaging, and the like, there is a demand to arbitrarily set an imaging section in real time, and technical development corresponding to this is being performed. There is an example in which an MRI image is displayed on the graphical user interface and the next section is determined by clicking a button on the screen as a method for arbitrarily selecting the section (Magnetic Resonance in Medicine: Rea1-time interactive) MRl on a conventional scanner; AB. Kerr et al., 38, pp. 355-367 (1997)). Another method is to use a 3D mouse (USP-5512827). In addition, an apparatus for determining an MRI imaging cross section using a position determination device is disclosed (USP-5365927: MRI imaging is performed using information from a position sensor), (USP-6026315; two infrared cameras) And the cross section is determined using a pointer consisting of three reflecting spheres).
[0059]
A technique of irradiating convergent ultrasonic waves and heating the inside of a living body in an ultrasonic device is known. For example, Japanese Patent Laid-Open No. 2001-46387 discloses an ultrasonic therapy applicator that treats a treatment site in a subject while constantly monitoring the treatment site with an ultrasonic image.
[0060]
In addition, it is known that a technique for monitoring a heated part in a living body is possible by MRI. That is, in MRI, the temperature in a living body can be monitored, and this function is used to monitor laser irradiation treatment and RF (Radio Frequency) ablation.
[0061]
Various proposals have been made for methods of temperature monitoring, but the following signal intensity method and phase method (PPS method: proton phase shift) have been studied extensively.
(1) Signal intensity method: It is known that the T1 value changes when the temperature of the subject changes. In addition, when the temperature is locally high as in the laser transpiration method, the T2 value of the living body and the water content change, and the signal value changes. From this change, the temperature change in the living body can be grasped qualitatively.
(2) Phase method: The resonance frequency of proton is proportional to temperature. The temperature coefficient C is −0.01 (ppm / ° C.). When the phase difference between two images taken before and after heating the living body in the GrE system sequence is obtained, the phase θ (i, j) (rad) (i and j are pixel numbers) after the difference is expressed by the following formula (1 ).
[0062]
θ (i, j) = γ · Bo · C · ΔT (i, j) · τ (1)
Here, γ is the magnetic rotation ratio, Bo is the static magnetic field strength, ΔT (i, j) is the temperature change of the living body before and after heating, and τ is the echo time. From the equation (1), a temperature change image is obtained by the following equation (2). A two-dimensional color map is used to display the temperature change image.
[0063]
ΔT (i, j) = θ (i, j) / (γ · Bo · C · τ) (2)
On the other hand, in MRA angiography (MRA), the maximum intensity projection (MIP) method is used as a method for displaying a three-dimensional structure from a phase image. Has been. Recently, a volume rendering (VR) method has also been attempted.
[0064]
Known examples of temperature images include, for example, authors: Paul Steiner MD, Rene Botnar PhD, Benjamin Dubno MD, Gesine G Zimmermann MD, G Scott Gazelle MD, Jorg F Debatin MD. Title: Radio-frequency-induced thermoablation: monitoring with T1-weighted and proton-frequency-shift MR imaging in an interventional 0. 5-T environment. Journal name: Radiology 206, 803-810, March (1998).
[0065]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a composite medical device excellent in operability and functionality by combining the advantages of an ultrasonic medical device and an MRI device.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram of an embodiment of an ultrasonic-magnetic resonance composite medical device according to the present invention.
FIG. 2 is an external configuration diagram of an embodiment of the ultrasonic-magnetic resonance composite medical device of the present invention.
FIG. 3 is a plan view for explaining a setting method of the position detection device according to the embodiment of the ultrasonic-magnetic resonance composite medical device in FIG. 2;
FIG. 4 is a configuration diagram illustrating a typical example of a magnetic resonance apparatus.
FIG. 5 is an explanatory diagram of a convergence point of a treatment probe.
FIG. 6 is a diagram illustrating a three-dimensional imaging operation in ultrasonic imaging.
FIG. 7 is a diagram illustrating an example of generating a composite image of an ultrasonic imaging apparatus and an MRI apparatus.
[Explanation of symbols]
1 Ultrasonic probe
2 Imaging probe
3 treatment probe
4 Probe support
12 therapeutic wave convergence circuit
13 Imaging wave convergence circuit
26 US signal processor
27 US image generator
28 US monitor
30 US control unit
41 MR device body
42 MR controller
44 MR signal processor
45 MR image generator
46 MR monitor
51 Detection pointer
52 Reference pointer
53 Compound Eye Camera
54 Probe position calculation means
55 Cooperative control means

Claims (8)

US control means for driving an ultrasonic probe to irradiate a subject with imaging ultrasonic waves and processing an ultrasonic signal received by the ultrasonic probe, and a tomography based on the received ultrasonic signal An ultrasonic medical device having US image generation means for generating an image;
MR control means for executing an imaging sequence for applying a gradient magnetic field and a high-frequency pulse to the subject placed in a static magnetic field according to a set tomographic plane, and a nuclear magnetic resonance signal generated from the subject by execution of the imaging sequence A magnetic resonance imaging apparatus having MR image generation means for generating a tomographic image based on
At least one display means for displaying an image generated by the US image generation means and the MR image generation means ;
A detection pointer of a position and orientation fixed to the ultrasonic probe, a reference pointer fixed to the main body of the magnetic resonance imaging apparatus, and a camera arranged to receive the detection pointer and the reference pointer And probe position calculation means for converting the position and orientation of the ultrasonic probe into the coordinate system of the magnetic resonance imaging apparatus based on the received image data of the camera,
Based on the position and orientation of the ultrasonic probe converted by the probe position calculation means and the focal position of the ultrasonic probe output from the US control means, a three-dimensional position of the lesion is obtained, and the lesion is An ultrasonic-magnetic resonance composite medical device that determines a tomographic plane to pass as the set tomographic plane of the MR image.   The ultrasonic-magnetic resonance composite medical apparatus according to claim 1, further comprising cooperative control means for outputting the determined set tomographic plane to the MR control means.   The MR control unit executes the imaging sequence for the determined set tomographic plane, detects a lesion part based on the MR tomogram displayed on the display unit by the execution, and based on the position of the lesion part 3. The ultrasonic-magnetic resonance composite medicine according to claim 2, wherein the position of the convergence point of the therapeutic ultrasound beam is calculated from the image data, and the calculated convergence point position is output to the US control means. apparatus.   The MR control unit executes the imaging sequence for the determined set tomographic plane, detects a mark representing a treatment point input and set in the MR tomographic image displayed on the display unit by the execution, and 3. The ultrasonic wave according to claim 2, wherein the position of the convergence point of the therapeutic ultrasound beam is calculated from the image data based on the position, and the calculated convergence point position is output to the US control means. Magnetic resonance composite medical device. The US control unit controls the convergence point position of the therapeutic ultrasound beam based on the input convergence point position of the therapeutic ultrasound beam, and responds to a given command from the ultrasound probe to the therapeutic ultrasound beam. Irradiate sound waves,
The MR control unit outputs a convergence point position of a therapeutic ultrasonic beam to the US control unit, and then executes a T1 or T2-weighted image imaging sequence for a tomographic plane including the convergence point. Item 5. The ultrasonic-magnetic resonance composite medical device according to Item 3 or 4.   The MR control means measures a temperature change of an MR tomogram based on image data of the T1 or T2 weighted image, and displays a color mapping image on the display device according to the temperature change. Item 6. The ultrasonic-magnetic resonance composite medical device according to Item 5. The US control means takes in the coordinate data of the position and orientation of the ultrasonic probe converted into the MR coordinate system output from the cooperative control means, and corresponds the MR coordinate data to the image data of the ultrasonic three-dimensional tomographic image. Let me remember,
The MR control means executes an imaging sequence for imaging an MR three-dimensional image of a region corresponding to the ultrasonic three-dimensional tomographic image, extracts a boundary of a specific tissue based on the MR three-dimensional image, and relates to the boundary 3. The ultrasonic-magnetic resonance composite medical apparatus according to claim 2, wherein image data is output to the display means and displayed superimposed on the ultrasonic three-dimensional tomographic image. The US control means takes in the coordinate data of the position and orientation of the ultrasonic probe converted into the MR coordinate system output from the cooperative control means, and corresponds the MR coordinate data to the image data of the ultrasonic three-dimensional tomographic image. Let me remember,
The MR control unit executes an imaging sequence for capturing an MR three-dimensional image of a region corresponding to the ultrasonic three-dimensional tomographic image, extracts a specific tissue boundary based on the MR three-dimensional image, and extracts the US control unit. Output to
The said US control means extracts the pixel data of the said ultrasonic three-dimensional tomogram within the boundary of the specific tissue extracted by the said MR control means, It displays on the said display means. The ultrasonic-magnetic resonance composite medical device described.

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